// 引入 fs 模块
const fs = require(`fs`)

// fs.readFile(`./resources/为学.md`, (err, data1) => {
//     fs.readFile(`./resources/插秧诗.md`, (err, data2) => {
//         fs.readFile(`./resources/观书有感.md`, (err, data3) => {
//             let result = data1 + `\r\n` + data2 + `\r\n` + data3;
//             console.log(result);
//         })
//     })
// })

// 使用 promise 实现
const p = new Promise((resolve, reject) => {
    fs.readFile(`./resources/为学.md`, (err, data) => {
        resolve(data)
    })
})

p.then(value => {
    return new Promise((resolve, reject) => {
        fs.readFile(`./resources/插秧诗.md`, (err, data) => {
            resolve([value, data])
        })
    })
}).then(value => {
    return new Promise((resolve, reject) => {
        fs.readFile(`./resources/观书有感.md`, (err, data) => {
            // 压入
            value.push(data)
            resolve(value)
        })
    })
}).then(value => {
    console.log(value.join(`\r\n`));
})